Fluid pump and high-pressure fuel feed pump

ABSTRACT

A fluid pump, wherein a cylinder supporting a plunger and a pump housing are formed with dissimilar metals and a pressing mechanism to press the cylinder and the pump housing relatively to each other is provided so that a pressurizing chamber is sealed through a pressing surface between the pump housing and the cylinder, whereby the number of seal points can be reduced and a reduction in reliability can be eliminated while realizing a reduction in weight of the pump housing and a reduction in cost due to increase in cutting capability using a soft member such as aluminum alloy for the pump housing.

TECHNICAL FIELD

[0001] The present invention relates to a pump that transports the fluid. For example, the present invention is suitable for the so-called high-pressure fuel (gasoline) supply pump to feed a high-pressure fuel forcefully for the fuel injection valve of the system that supplies the fuel (gasoline) directly to the combustion chamber of the internal combustion engine.

BACKGROUND ART

[0002] In the conventional device, a hollow cylindrical part is provided in a pump housing (called a body or a base) of the pump as a first member. A cylinder (called a plunger support member, a plunger slide tube or a cylindrical member) as a second member is made to fit the hollow cylindrical part. The pressurizing chamber that pressurizes the fuel is formed by closing the open end of the cylinder using a seal plate. The reciprocation plunger whose point goes into and out from said pressurizing chamber is supported by this second member so as to go into and out from there.

[0003] For instance, such a conventional device is proposed as a high-pressure fuel feed pump for an internal combustion engine in the Japanese Patent Application Laid-Open No. 11-82236.

[0004] A high-pressure fuel feed pump which can decrease the processing man-hour ruining neither wear and abrasion resistance nor liquid seal properties by making the second member which maintains the plunger slidably of the metal member of wear and abrasion resistance, and by making the first member into which the second member is inserted of the metal member of non-wear and abrasion resistance like an aluminum alloy is described in this document.

[0005] However, in this prior art, the pressurizing chamber and the low-pressure chamber are sealed by pressing a seal plate provided at the open end of the cylinder against the cylinder end surface. Further, the first member and the second member are almost closely contacted in the opening area of the periphery of the second member. Therefore, the difference of the heat deformation amount is caused according to the difference of the thermal expansion coefficient between both members. As a result, the problem that the cylinder receives the stress and deforms locally when both members expand due to the effect of heat, and the plunger gnaws at the cylinder is occurred. Further, the space between the plunger and the cylinder wall surface is about five microns. An average thermal expansion coefficient of the aluminum alloy member is 23×10⁻⁶. Moreover, an average thermal expansion coefficient of an iron system member is 10×10⁻⁶ for steel, and 17×10⁻⁶ for SUS. If the diameter (inside diameter or outside diameter) is 30 Φ, the thermal expansion of 7 microns, 3 microns, and 5 microns is caused respectively because the amount of the thermal expansion is obtain ed by diameter×thermal expansion coefficient×temperature variation difference. This thermal expansion acts on the outside wall of the cylinder, and causes the deformation of the cylinder.

[0006] Moreover, because it is necessary to assemble so that they should not come off with many seal rings installed between the first member and the second member, the assembly work of the first member and the second member is bad, and not practicable.

[0007] Further, the member named a plunger in the above-mentioned prior art might be named a piston or a reciprocating rod in other documents. The plunger used in the present invention means the same one as these members. Of course, it is possible to catch functionally as the element by which the fluid is pressurized. Therefore, not only the rod shape one but also the expression of pressurizing element to have the function to compress the fluid are also used.

[0008] Not only the one of the rod shape described in the embodiments but also the element of the shape having the pressurizing function not described in the embodiments are included in the technology range of “Pressurizing element” in this application.

DISCLOSURE OF INVENTION

[0009] An object of the present invention is to provide a high-pressure fuel feed pump with few seal parts between the first member and the second member, maintaining the merit of the above-mentioned prior art that the processing man-hour can be decreased with neither the abrasion resistance, nor liquid seal properties being ruined.

[0010] Moreover, another object of the present invention is to provide a high-pressure fuel feed pump that regardless of the quality of material of the first member and the second member but the assembly character of both members is excellent.

[0011] A further object of the present invention is to decrease the contact part of the pump housing and the cylinder formed by members with a different thermal expansion coefficient, suppress the generation of the local stress caused by the difference of the amount of the thermal expansion, and control the deformation of the cylinder.

[0012] A further object of the present invention is to provide a high-pressure fuel feed pump wherein there is no need to make the discharge opening to discharge the high-pressure fluid for the cylinder made of the hard metal.

[0013] To achieve at least one of the above-mentioned objects, pressing mechanism is provided to press the first member and the second member on the surface that intersects with the direction where the plunger goes into and back from (preferably, the surface perpendicular to the direction of going in and out) in the present invention. The metal seal by the pressure-contact of both metals or the metal seal where another metallic component is inserted is formed on this pressure-contact surface. The pressurizing chamber formed between the first member and the second member is sealed up in this metal seal.

[0014] As a result, an excellent seal performance can be obtained providing neither the seal ring nor the gasket between the first member and the second member. The assembly work becomes very easy.

[0015] Because adhesion is not demanded on opposing surfaces of both members (especially, surroundings side) except the pressure-contact surfaces or this sealing part, an enough space can be given. As a result, even when both members are formed of the member with a different thermal expansion coefficient, the stress by a partial thermal expansion difference is not generated easily.

[0016] Moreover, as the mechanism that easily assembles the second member to the first member, the mechanism that houses the second member in the holder with the screw and screws it to the first member is proposed in the present invention.

[0017] Specifically, it is convenient if this mechanism composes the pressing mechanism.

[0018] In addition, the configuration by which the generation of the stress by the thermal expansion difference between the first member and the second member is controlled is also proposed in the present invention.

[0019] Therefore, a concave part for the pressurizing chamber is formed in the pump housing in the present invention. The pressurizing chamber is formed by sealing up the opening of this concave part with the cylinder. The pump case and the cylinder need not come in contact in the part other than the contact part in the sealing surface if they are composed like this. Therefore, the local generation of the thermal stress can be reduced even when the members with a different thermal expansion coefficient are used for both members, and the deformation of the cylinder can be controlled.

[0020] Because the intake valve mechanism of the pump and the delivery valve mechanism are installed in the pump housing in another invention of this application, the openings for the discharge port and the inlet port comes to be able to form in the pump housing formed of a comparatively soft metallic member. As a result, the processing is improved very much.

[0021] The fluid transportation pump is targeted widely for the technology not pointed especially in the present invention, and the peculiar technology for a high-pressure fuel pump is explained pointing out so.

BRIEF DESCRIPTION OF DRAWINGS

[0022]FIG. 1 is a vertical sectional view of a high-pressure fuel feed pump according to one embodiment of the present invention.

[0023]FIG. 2 is an exploded perspective view of a high-pressure fuel feed pump of FIG. 1.

[0024]FIG. 3 is a partially enlarged view of FIG. 2.

[0025]FIG. 4 is a view to explain the feature of this embodiment.

[0026]FIG. 5 is a vertical sectional view of a high-pressure fuel feed pump of another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0027] The configuration and the operation of one embodiment of a high-pressure fuel feed pump that adopts the present invention are explained with reference to FIG. 1 and FIG. 2. This high-pressure fuel feed pump is regarded as a fluid transportation pump that handles gasoline pressurized from 5 to 20 mega Pascal as the pressurizing fluid. Therefore, this differs from the one to handle the high-pressure fluid more than 100 mega Pascal like a high-pressure fuel pump for a compression ignition oil engine. Moreover, this differs in the condition from a feed pump where the fluid is transported by pressure that is slightly higher than the atmospheric pressure.

[0028] Further, this differs from the device that compresses the gas like the compressor at the refrigerating cycle.

[0029]FIG. 1 is a vertical sectional view of the entire pump and FIG. 2 is an exploded perspective view of the pump shown in FIG. 1.

[0030] Pump p is provided with a pump housing 1 (called a body or base) as a first member and a cylinder 20 (called a plunger support member, a plunger slide tube, or a cylindrical member) as a second member.

[0031] The pump housing 1 is made of the light member softer (the hardness is low, for instance, 45-70 in HRB) than the stainless steel and the iron system member like tool steel, as well as the aluminum or the aluminum alloy (for instance, JIS standard A2017, ADC12, or AC4C). In addition, the member shows non-abrasion resistance and large thermal expansion coefficient (23×10⁻⁶ or more, for instance).

[0032] The cylinder 20 is made of hard heavy-weight alloy (hardness is high, for instance, 200 or more in HRB) with abrasion resistance as well as stainless steels and tool steels, and small thermal expansion coefficient (for instance, 17×10⁻⁶ or less in SUS, and 10×10⁻⁶ in iron).

[0033] The cylinder 20 is assembled into the pump housing 1 in such a way that an annular plane 20A formed in the periphery of cylinder 20 contacts to an annular plane 122 at the open end of concave part 121 of pump housing 1, which has the bottom. Consequentially, both form the metal interface of the aluminum material and the iron-system material on the annular planes.

[0034] A through tube 201 in which plunger 2 is inserted is formed at the center of cylinder 20. A plunger 2 is supported to be able to slide in this through tube 201, and plunger 2 can go in and out axially therefore.

[0035] Thus, bottom-having concave part 121 of pump housing 1 forms space 12 from which plunger 2 goes into and back from between the point of cylinder 20 and itself. The space 12 functions as a pressurizing chamber to pressurize the fuel fluid inhaled there by plunger 2. The hardness of cylinder 20 is higher than that of the pump housing 1 as described above. Moreover, the annular plane 122 of pump housing 1 and the annular plane 20A of cylinder 20 is relatively pressed by the pressing mechanism described later. Therefore, the annular plane 122 of pump housing 1 is made plastic deformation at the part where the annular plane 20A of cylinder 20 is contacted. Both are strongly pressed in that part, and the seal by the surface contact of the metal is formed.

[0036] Thus, space 12 from which plunger 2 goes into and back from is formed as a closed chamber divided with intake valve, the delivery valve, and this seal. As a result, it is possible to act as pressurizing chamber 12 of the fuel pump.

[0037] A fuel inlet port 10 and a discharge port 11 are formed in the pump housing 1 made of the aluminum alloy. The fuel inlet port 10 is connected to the pressurizing chamber 12 through inlet chamber 10 a and inlet port 10 b.

[0038] The discharge port 11 is connected to pressurizing chamber 12 a through discharge port 11 b. A delivery valve unit 6 explained later in details is installed in discharge port 11.

[0039] Inlet chamber 10 a and inlet port 10 b are formed by cutting or drilling pump housing 1 made of the aluminum alloy.

[0040] The cylindrical processing opening 10A with larger diameter than inlet port 10 b is formed at the entrance of inlet port 10 b formed as a through tube with small diameter.

[0041] A cylindrical intake valve unit 5 is installed in this the cylindrical processing opening 10A.

[0042] Intake valve unit 5 has the intake valve holder 5A with a disk bottom and a cylinder wall in the surroundings, intake valve 5C with a disk bottom opposite to said holder 5A and a cylindrical wall in the surroundings. Spring 58 that consists of the coil spring is installed between the opposed bottoms of the intake valve holder 5A and the intake valve 5C.

[0043] A plurality of through tubes 5D is provided at a suitable interval in the disk bottom of the intake valve holder 5A (one of them appears in FIG. 3).

[0044] The intake valve holder 5A is made of the stainless steel. Pressure-contact surface 10B between this holder and pump housing 1 forms a seal part by the surface contact of metals as well as the pressure-contact surface between the pump housing 1 and the cylinder 20.

[0045] A valve seat member 200A contact so as to close the open end of the intake valve holder 5A.

[0046] A through tube 200B which connects the inlet chamber 10 a and the inlet port 10 b is formed at this center of the seat member 200A.

[0047] This through tube 200B can be blockaded by the intake valve 5C that is energized by a spring 58.

[0048] The annular projection 5E of is formed in the end surface faced to the seat member 200A of the intake valve 5C. This annular projection 5E is arranged concentrically in surroundings of through tube 200B at the center of the seat member 200A. This annular projection 5E contacts to the end surface of the seat member 200A, and through tube 200B is blockaded.

[0049] The seat member 200A is installed at the point of electromagnetic plunger mechanism 200.

[0050] Electromagnetic plunger mechanism 200 is installed in cylindrical concave part 200D formed in the pump housing 1 by the cutting work. Threaded part 200C is formed in the inner wall of cylindrical concave part 200D. Electromagnetic plunger mechanism 200 is assembled in a holder 201 with screw engaged to this threaded part 200C.

[0051] A fixed ring 200E is installed in the annular groove formed in the periphery of the electromagnetic plunger 200. The outer corner part of this ring 200E is connected to the annular concave part formed inside the point of holder 201.

[0052] Thus, electromagnetic plunger 200 is installed in holder 201 with the screw. When the nut 201A of holder 201 with the screw is rotated, the seal member 200A is pressed against intake valve unit 5 through a ring 200E engaged to the annular concave part of the holder 201. After that, intake valve unit 5 is pressed against the pump housing 1, and these parts are installed in pump housing 1.

[0053] At this time, it is possible to adjust the power by which the seat member 200A installed at the point of electromagnetic plunger mechanism 200 press the intake valve unit 5 against pump housing 1 by adjusting the tightening power of the nut 201A.

[0054] And, this power contributes to the formation of the seal by the metallic pressure-contact between the intake valve unit 5 and the pump housing. Therefore, the holder 5A of the intake valve unit 5 is formed with harder material than the aluminum alloy like stainless steel.

[0055] The electromagnetic plunger mechanism 200 is in a turn-off state, the movable plunger 202 resists the power of spring 5B by using a spring 203 and maintains the intake valve 5 in opening position.

[0056] At this time, the movable plunger 202 of the electromagnetic plunger mechanism 200 extends via the through tube 2008 of the seat member 200A to the intake valve 5C. The plane part of hemispherical ball 202A provided at the point of movable plunger 202 contacts to the intake valve 5C. Further, the spring 5B is pushed, and the intake valve 5C is pulled apart from the seat member 200A. As a result, the inlet chamber 10 a and the intake port 10 b are led via the through tube 5D and the through tube 200B.

[0057] The movable plunger 202 resists the power of spring 203 at the turn-on of electromagnetic plunger mechanism 200 and is attracted. At this time, the intake valve 5C is controlled to the closed position or the open position in accordance with the relationship between spring 5B and the pressure difference of the fuel in the upstream and downstream of the intake valve 5C. The inlet port 10 that leads to inlet chamber 10 a is formed in the pump housing 1. Moreover, filter unit 10 f is installed between the inlet port 10 and the inlet chamber 10 a.

[0058] A dumper chamber 10 e that leads to inlet chamber 10 a is formed in the periphery of the pressurizing chamber 12 of the pump housing 1.

[0059] The dumper chamber 10 e is closed with a shutting lid 110C fastened to pump housing 1 with screw 1108 through aseal ring 110A. Dumper mechanism 110 that adjusts the pressure of the dumper chamber 10 e is installed in the shutting lid 110C. The dumper chamber in the dumper mechanism 110 leads to dumper chamber 10 e on the side of the pump housing 1 through the shutting lid 110C.

[0060] The one edge of the discharge port 11 b of which the other edge leads to the pressurizing chamber 12 is open in discharge port 11 formed in the pump housing 1.

[0061] The discharge port 11 is formed in the pump housing 1 as a larger hall 11D than the diameter of discharge port 11 b. A threaded part 101C is formed in a surrounding wall of the hall 11D.

[0062] A discharge port unit 6 is installed in this discharge port 11.

[0063] The delivery valve unit 6 includes a ball valve 11E energized by the spring in the metal nipple 6A.

[0064] A screw 6B is formed inside of one edge of the metal nipple 6A. The fuel piping not shown in the figure is connected with this screw 6B.

[0065] Moreover, a screw 11C connected with the threaded part 101C formed in pump housing 1 is provided outside of the metal nipple 6A.

[0066] The fuel passage with a small diameter penetrates to an internal center of the metal nipple 6A, and the step part is formed in the surroundings.

[0067] A flanged and cylindrical spring bearing 11H are installed in the fuel passage, and the flange part contacts to said step part.

[0068] One edge of the spring 11A is received by this flange part.

[0069] The other edge of the spring 11A is supported in the peripheral step of the valve suppression 11B.

[0070] A valve guard 11B is an elongated and solid tube, and a plurality of communicating grooves 11J are formed in an axial direction and in a circumferential direction. When the delivery valve 11E opens, the fuel flows from the discharge port 11 b to discharge opening 11 a through this communicating groove 11J.

[0071] Although the delivery valve 11E is always energized in the closed direction by the spring 11A, delivery valve 11 is open when the pressure in the pressurizing chamber 12 exceeds the thrust-pressure power of the spring 11A and the fuel pressurized to the high pressure is discharged from the discharge port 11 (discharge opening 11 a).

[0072] Pressurizing chamber 12 includes the passage to intake valve 5 including the inlet port 10 b, and the passage to the delivery valve 11E including the discharge port 11 b.

[0073] A valve seat 11G and a seal ring 11F are arranged concentrically in order from the inside between the delivery valve unit 6 and the pump housing 1.

[0074] The valve seat 11G and the seal ring 11F are interposed between the pump housing 1 and the point of the delivery valve units 6 by the pressing power generated in a axial direction when the screw 11C for delivery valve unit 6 is inserted into the threaded part of pump housing 1.

[0075] The size of the edge of discharge port 11 b of the delivery valve unit 6 is set so that the inside diameter may be smaller than the outside diameter of the valve seat 11G and the outside diameter may be larger than the inside diameter of the seal ring 11F.

[0076] As a result, both valve seat 11G and seal ring 11F can be pressed against the pump housing by one ring part at the point of the delivery valve unit 6.

[0077] Here, the valve seat 11G is formed with the steel member. Moreover, the seal ring 11F is formed with soft metal material like the aluminum alloy or the gasket. Because the first seal formed by the metal surface contact of the valve seat 11G and the pump housing 1 and the second seal formed with the seal ring 11F and the pump housing 1 in the periphery of the first seal exist in such seal structure, the seal becomes certain.

[0078] Concretely, even when the cavitation generated by the collapse of the void of a high-pressure fuel acts between the contact surface of the first seal formed by the metal surface contact of the valve seat 11G and the pump housing 1, the pump housing of soft metallic is invaded, and the first seal is broken, it is possible to prevent the leakage to the outside by the second seal.

[0079] The reliability to the destruction of the seal of the delivery valve improves because the first seal becomes a protector even in such a state and the cavitation of the pressurizing fuel does not reach the second seal.

[0080] Because the fuel leaks directly to the atmosphere by the seal destruction in the delivery valve, the improvement of reliability to the seal destruction in the delivery valve in this embodiment provides an important effect.

[0081] The assembly mode of the pump housing 1 and the cylinder 20 is explained next in details.

[0082] A cylindrical surrounding wall 124 with larger diameter than the diameter of the concave part 121 having a bottom is provided on the open end side of the concave part 121 (which forms the pressurizing chamber for the pump) of pump housing 1.

[0083] As a result, the steps part is caused between the cylindrical surrounding wall 124 and the concave part 121, and an annular plane 122 is formed therein.

[0084] Moreover, a screw groove 18 is formed in the inside part of the cylindrical surrounding wall 124.

[0085] Plunger 2 is inserted in a through tube 201 provided at the center of cylinder 20, and is supported slidably.

[0086] As a result, the plunger 2 is supported by cylinder 20, the reciprocation is permitted, and its point goes into and back from in the pressurizing chamber 12.

[0087] The cylinder 20 is formed cylindrically as a whole, and the outside diameter at the point of the pressurizing chamber side point is smaller than the diameter of the surrounding wall in the bottom-having concave part of the pump housing 1. The outside diameter of the middle part of the cylinder 20 is larger than the inside diameter of the annular plane 122 of the pump housing 1.

[0088] Therefore, the step part is made between the point part and the middle part located on the pressurizing chamber side in the periphery of the cylinder 20, and the annular plane 20A is formed therein.

[0089] This annular plane 20A is defined as a plane that intersects in a shift direction of the plunger 2. This plane can be made not only as the perpendicular plane with respect to a center axle of plunger 1 but also as an inclined plane if it is necessary for the practical use.

[0090] A similar step part is formed at the edge on the opposite side of cylinder 20, and annular plane 20B is formed therein.

[0091] Cylinder 20 is assembled in the pump housing with it being housed in cylinder holder 21.

[0092] Therefore, screw 21B is formed outside of cylinder holder 21. The annular plane 21A of which the diameter is smaller than the outside diameter of annular plane 20B of cylinder 20 is formed on the inside.

[0093] The cylinder 20 is supported in the cylinder holder 21 by the contact of the annular plane 20B and the annular plane 21A of the cylinder holder 21 when the cylinder 20 is inserted in the cylinder holder 21.

[0094] When the threaded part 21B of the cylinder holder 21 is connected to the threaded part 1B of the pump housing 1, the cylinder 21 is fixed to the pump housing 1 with the cylinder 21 being interposed between the annular plane 122 of the pump housing and the annular plane 20B of the cylinder holder 21.

[0095] At this time, the relative thrust-pressure power between the annular plane 122 of the pump housing 1 and the annular plane 20A of the cylinder 20 can be adjusted to thrust-pressure power suitable to form the seal by adding and subtracting the screw fastening power to the pump housing 1.

[0096] The phenomenon that the difference of the amount of thermal deformation caused in an axial direction by the difference of the thermal expansion coefficients of the pump housing 1 and the cylinder 20 deteriorates the sealing properties of both is improved in this embodiment. The mechanism of the improvement is explained in details with reference to FIG. 4 hereafter.

[0097] The distance between the pressure-contact surface S1 of the pump housing 1 and the cylinder 20, and the pressure-contact surface S2 of the pump housing 1 and the cylinder holder 21 is LI. On the other hand, the distance between the pressure-contact surface SI of the pump housing 1 and the cylinder 20, and the middle point of screw fastening part P1 of the pump housing 1 and the cylinder holder 21 is L2.

[0098] Here, the screw fastening part PI is provided at the position where these two distance LI and L2 satisfy the relationship of LI>L2 in this embodiment.

[0099] Because the members with a different coefficient of linear expansion (aluminum material>steel material) are used in this embodiment wherein the aluminum material is used for pump housing 1 and the steel material is used for cylinder 20 in this embodiment, an amount of the thermal expansion generated in an axial direction of the pump housing is larger than that of the cylinder. Therefore, the difference (ΔLI−ΔL2) of both amounts of the expansion can increase if both distance LI and L2 are equal, the space occurs in the pressure-contact surfaces SI and S2, and the seal decreases.

[0100] Then, the difference (ΔLI−ΔL2) of both amounts of the expansion is decreased by assuming LI>L2 in this embodiment as described above. As a result, part, the generation of the space in the pressure-contact parts SI and S2 is suppressed, and the seal is prevented being decreased.

[0101] The aluminum alloy of which the thermal expansion coefficient is about 23×10⁻⁶ (for instance, JIS standard A2017, ADC 12, AC4C) is used for the pump housing 1 of this embodiment. Moreover, the tool steel of which the thermal expansion coefficient is 10×10⁻⁶ is used for cylinder 20.

[0102] Therefore, the both amounts (Δ1, Δ2) of the thermal expansion are calculated as follows when there is a temperature change of 100° C.

Δ1=LI×10×10−6×100(° C.)

Δ2=L2×23×10−6×100(° C.)

[0103] Both thermal deformation amounts Δ1 and Δ2 can be almost made equal here by setting to become LI=2×L2. The thermal expansion difference is not generated even if there is a temperature change, and the seal is ruined because the space is not made in the pressure-contact surfaces SI and S2.

[0104] There are provided gap GI between the outside of the point of cylinders 20 on the pressurizing chamber side and the inside of pump housing 1, gaps G2 and G5 between the inside diameter side of cylinder holder 21 and the outside of the cylinder 20, and gaps G3 and G4 between the inside of the pump housing 1 and the outside of the cylinder holder 21 so that neither pump housing 1 nor cylinder 20 may come in contact directly in a radial direction.

[0105] The cylinder holder 21 and the cylinder 20 have an circumferential engagement part QI for positioning in a radial direction. The position of the circumferential engagement part PI and that of the screw fastening part P1 of the cylinder holder 20 and the pump housing 1 are displaced so as not to overlap in a direction along the cylinder axle line. Namely, the gap G2 is provided inside the screw fastening part P1 and the gap G3 is provided outside the circumferential engagement part QI.

[0106] The threaded part of the cylinder holder 21 is deformed internally within the range of the gap G2 when the pump casing 1 is deformed by the thermal expansion internally, and the influence due to the deformation of the cylinder holder 21 does not reach the circumferential engagement part QI.

[0107] The screw fastening part PI is provided on the open-end side of the cylinder holder 21 from the circumferential engagement part QI in this embodiment.

[0108] Moreover, because the wall thickness of cylinder holder 21 at screw fastening part PI is thinner than the wall thickness in the screw engagement part PI in this embodiment, the deformation due to the thermal expansion of the pump casing 1 is absorbed by deforming the screw fastening part PI, and the influence on the circumferential engagement part QI is controlled. Moreover, a little space is provided at the circumferential engagement part QI within the range where the positioning of cylinder 20 in a radial direction is not prevented.

[0109] This configuration is effective in the control of the tightening power which acts on the cylinder 20 when the screw fastening part PI is deformed into the direction of the inside diameter by the thermal expansion of the pump housing 1 while securing the coaxiality of the cylinder holder 21 and the cylinder 20.

[0110] Thus, the space in the sliding area of the cylinder 20 and the plunger 2 can be kept proper, and the burning or the biting of plunger 2 can be prevented according to the above-mentioned configuration.

[0111] Moreover, because the material whose thermal conductivity is smaller than the pump housing 1 (The stainless steel member is used in this embodiment) is used for cylinder holder 21, the heat of pump housing 1 is not transmitted easily to cylinder 20. Therefore, this configuration also has the effect of the control of the burning of the plunger 2.

[0112] In addition, the resin coating is given to the threaded part of the cylinder holder 21. The heat transfer from the pump housing 1 is decreased further by this configuration.

[0113] Moreover, an annular low-pressure chamber 10 c that leads to an inlet chamber 10 a through a passage 10 d is provided outside of cylinder 20.

[0114] As a result, the heat transfer from the pump housing 1 to the cylinder 20 is decreased, and cylinder 20 is cooled by the fuel.

[0115] Moreover, a plunger seal 30 by which the fuel outflow from the sliding area of plunger 2 to the cam 100 side is prevented and the leakage of oil from the cam side to the plunger sliding area is sealed is supported inside cylinder holder 21.

[0116] Because the cylinder 20 and the plunger seal 30 are connected to the cylinder holder 21 of the same member, the plunger seal 30 and the plunger 2 that is the sliding member are supported in the same axis. As a result, the seal in the plunger sliding area can be kept excellently.

[0117] Moreover, a plunger seal chamber 30 a formed on the cylinder open end side of the plunger seal 30 (inside part of the pump) is connected with the fuel bank 20 a provided in the cylinder 20 through space X in the sliding area of the cylinder 20 and plunger 2, and is connected with the annular chamber 10 c through a passage 20 b, a hollow 10 f, and a passage 20D.

[0118] A plunger seal chamber 30 a where the atmospheric pressure acts on and a low pressure chamber connected with inlet chamber 10 a which consists of the hollow 10 f, the passage 20D, and the annular chamber 10 c provided in the neighborhood of cylinder 20 are divided.

[0119] Moreover, the plunger seal chamber 30 passes the communicating opening 21 a provided in the cylinder holder 21, the annular chamber log formed in the periphery of the positioning part QI of the cylinder holder 21 and the passage 121 a provided in the pump housing 1, and leads to a return pipe 40.

[0120] The return pipe 40 is connected to the fuel tanks 50 about in the atmospheric pressure through the return piping not shown in the figure. Therefore, the pressure of a plunger seal chamber 30 a is almost equal to fuel tank pressure, or the atmospheric pressure because it leads to the fuel tank 50 through the return pipe 40.

[0121] The fuel that leaks from pressurizing chamber 12 through sliding space X between the cylinder 20 and the plunger 2 flows from the fuel bank 20 a to inlet chamber 10 a side through the passages 20 b and 20D.

[0122] Because the pressure of a low-pressure fuel is applied from the inlet chamber 10 a to the fuel bank 20 a, the pressure is higher than plunger seal chambers 30 a at the atmospheric pressure through sliding space X. Therefore, the fuel flows from the fuel bank 20 a to the plunger seal chamber 30 a at the atmospheric pressure. This fuel flows to the fuel tank 50 through the return pipe 40. However, it is easy to make the fuel a gas because the plunger seal chamber 30 a at the high temperatures is almost at the atmospheric pressure.

[0123] In this embodiment, the distance LX of the sliding space X from the fuel bank 20 a to the opening of the cylinder 20 on the plunger seal 30 is shorter than the reciprocating and sliding length of the plunger.

[0124] As a result, the fuel adhered to plunger 2 in fuel bank 20 a when plunger 2 is located at the top dead point passes the cylinder opening 20 d when the plunger 2 is located at the bottom dead center. Therefore, the oil film is secured at the cylinder opening 20 d, the lubricity is improved, and the wear of the cylinder 20 and the plunger 2 can be decreased.

[0125] Moreover, a throttle part 21b is provided between the plunger seal chamber 30 a and the return pipe 40.

[0126] The fuel becomes easy to stay in the plunger seal chamber 30 a by restricting the flowing amount of the fuel to the fuel tank 50 from the plunger seal chamber 30 a. As a result, it is possible to improve the abrasion resistance of the plunger seal 30 and the cylinder opening 20 by the fuel. Especially, it is effective when the plunger seal 30 is in the upper part from the return pipe 40 when the pump is installed (The top and bottom is reversed in the direction shown in the figure).

[0127] A lifter 3 provided at the bottom of the plunger 2 is pressed against a cam 100 by the spring 4.

[0128] The lifter 3 resists the spring 4 and is pushed up when the cam 100 is rotated by the engine camshaft etc. and is depressed by the spring 4. Thus, the plunger 2 is supported by the cylinder 20. The plunger 2 slides into and back from in the through tube 201, and changes the capacity of the pressurizing chamber 12.

[0129] Moreover, plunger seal 30 that prevents the fuel from flowing out to the side of the cam 100 is provided to the bottom of cylinder 20.

[0130] The inlet chamber 10 a that are a low-pressure fuel chamber, annular low-pressure chamber 10 c that surrounds the seal part are provided through the intake valve holder 5A. Further, the dumper chamber 10 e is provided outside the upper wall of the pressurizing chamber 12.

[0131] The fuel does not leak outside the pump even if there is a fuel leakage from the seal with metallic pressure-contact of the metal interface of the cylinder and the pump housing.

[0132] Because the cylinder 20 is made of the material of high er hardness than the pump housing 1, cylinder 1 bites into the pressure-contact surface on the side of the cylinder 1, and the seal of the cylinder is improved.

[0133] Especially, the seal can be improved further by using the softness material like aluminum for the cylinder 1.

[0134] In the upper part of pumping chamber 12 a or a part of pressurizing chamber 12, the low-pressure chamber 10 f that leads to the inlet chamber 10 is provided. The wall 1 a is the most weakness part in all walls of pressurizing chamber 12.

[0135] That is, when the pressure of the pressurizing chamber pressure rises suddenly by some failures, this weakness part is destroyed first, and the high-pressure fuel is discharged into the dumper chamber 10 e. Therefore, also when the pressurizing chamber becomes an abnormal high pressure, the fuel can be prevented from leaking outside.

[0136] Moreover, a solenoid 200 that controls the opening and shutting time of the intake valve 5 is supported in inlet chamber 10 a by a solenoid holder 210 in this embodiment. Moreover, an annular fuel chamber is formed in the outer periphery of the solenoid coil between the solenoid 200 and the solenoid holder 210.

[0137] As a result, the solenoid 200 can be cooled with the fuel. It is possible to provide an annular fuel chamber in the outer periphery of the solenoid without using the solenoid holder.

[0138] Moreover, the heat transfer from the pump housing 1 to the solenoid 200 can be decreased by providing a threaded part in the outer periphery of the solenoid holder 210 and engaging it to the pump housing.

[0139] The heat of pump housing 1 does not transmit easily to the solenoid 200 by using the material with lower thermal conductivity than the pump housing 1 for solenoid holder 210, and solenoid 200 can be prevented from being damaged by a fire.

[0140] In addition, the heat transfer from the pump housing 1 can be decreased further by coating the resin to the threaded part of the solenoid holder 210.

[0141] Moreover, the impact force when turning off is decreased by gradually decreasing the driving current for the solenoid 200 when turning off, and the wear-out at the collision part and the breakage can be prevented.

[0142] In addition, the operation distance of the actuator of solenoid 200 is set to the distance shorter than the operation distance of the intake valve 5.

[0143] As a result, even when the operation time of solenoid 200 (response at OFF) is even of the slow situation, the intake valve is opened quickly at the change in the pressure of the pressurizing chamber (when shifting from the discharge process to the inlet process). Therefore, the opening space of the intake valve 5 can be secured enough, and the impact force can be decreased by reducing the operation distance of the solenoid 200.

[0144] The decrease in the pressure of the pressurizing chamber at the inlet process can be prevented because the passage resistance of the intake valve 5 is decreased by these means, and the generation of the cavitation can be controlled.

[0145] The backflow of the high-pressure fuel to the pressurizing chamber by the shutting delay of the delivery valve 6 (When shifting from the discharge process to the inlet process) can be suppressed to minimum by shortening the operation distance of the delivery valve 6 more than the intake valve 5, and the generation of cavitation in the pressurizing chamber can be controlled.

[0146]1C designates a seal ring that seals between the fluid pump and the engine body, and 21C designates a seal ring that seals between the pump housing 1 and the cylinder holder 21.

[0147] The outer periphery of cylinder 20 sealed by the seal ring 21C and the plunger seal 30 forms the inlet air passage 10 a, or the low-pressure chamber connected with a tank 50.

[0148] Therefore, even if the fuel leaks from the pressure-contact part of the pump housing 1 and the cylinder 20, the fuel does not leak directly to the atmosphere.

[0149] Even when the softness material like aluminum is used for the pump housing, the low-cost and lightening pump with a high degree of reliability by the improvement of cutting can be provided according to the present invention.

[0150] The point of a basic structural of this embodiment is explained with reference to FIG. 5.

[0151] A concave part (having a bottom) that becomes a pressurizing chamber is formed in the pump housing according to the first feature of this embodiment. The concave part is formed as a pressurizing chamber by installing the cylinder in the pump housing.

[0152] The cylinder and the pump housing only have to be pressed only in the seal part, and both need not come in contact especially in the circumferential direction according to this configuration. That is, there is an effect that the deformation of the cylinder caused by the difference of the amount of the thermal expansion when the pump housing and cylinder is configured by different material can be reduced.

[0153] A concave part (having a bottom) that becomes a pressurizing chamber and a low-pressure chamber is formed in the pump housing according to the second feature of this embodiment. The concave part is divided into the pressurizing chamber and the low-pressure chamber by installing the cylinder in the pump housing. The outside of the high pressure chamber is surrounded by the low pressure chamber with the effect of the above-mentioned first feature maintained by providing a seal mechanism between the opening part of the concave part of the pump housing and the plunger and connecting this low pressure chamber to the inlet passage or the fuel tank. As a result, the possibility that a high-pressure fuel leaks directly to the atmosphere can be reduced. 

1. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a plunger supported by the cylinder to reciprocate, which pressurizes fluid in a pressurizing chamber formed between said cylinder and said pump housing, a metal seal formed by pressing said pump housing and said cylinder at the plane intersecting in a shift direction of said plunger, a pressing mechanism that presses said pump housing and said cylinder relatively toward said metal seal.
 2. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a plunger supported by the cylinder to reciprocate, which pressurizes fluid in a pressurizing chamber formed between said cylinder and said pump housing, a metal seal formed by pressing said pump housing and said cylinder at the plane intersecting in a shift direction of said plunger, a pressing mechanism which presses said pump housing and said cylinder relatively so that both may be not in contact except at the seal part formed by said pump housing and said cylinder at the plane intersecting in a shift direction of said plunger.
 3. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a plunger that pressurizes the fluid in a pressurizing chamber formed between said cylinder and said pump housing, wherein a gap is provided between opposing surfaces in a radial direction of said pump housing and said cylinder.
 4. A fluid pump formed by forming a concave part in the pump housing, assembling a cylinder member to the opening of said concave part and forming said concave part as a pressurizing chamber, providing a intake valve mechanism which supplies fluid to the pressurizing chamber and a delivery valve mechanism which takes out the pressurized fluid from the pressurizing chamber to said pump housing, pressurizing the fluid in said pressurizing chamber by a reciprocation plunger supported by said cylinder.
 5. A fluid pump formed by forming a concave part in the pump housing, assembling a cylinder member to the opening of said concave part and forming said concave part as a pressurizing chamber, providing a intake valve mechanism which supplies fluid to the pressurizing chamber and a delivery valve mechanism which takes out the pressurized fluid from the pressurizing chamber to said pump housing, pressurizing the fluid in said pressurizing chamber by a reciprocation plunger supported by said cylinder, wherein said cylinder is installed in said pump housing by engaging a holder member into which said cylinder is housed to a threaded part of said pump housing.
 6. A fluid pump comprising; a metallic pump housing having a concave part, a screw groove formed to the inner wall of said metallic pump housing on the open-end side of said concave part, a holder member in which a threaded part that engages with the screw groove is formed in the outer periphery, a metallic tube body maintained in said holder member, which is assembled with said metallic pump housing to form said concave part as a fluid pressurizing chamber, and a plunger supported so as to be able to reciprocate, which goes into and back from said pressurizing chamber.
 7. A fluid pump comprising; a pump housing made of aluminum alloy having a concave part, in which the screw groove is formed on a surrounding wall of the open-end side of the concave part. a holder member engaged to said screw groove, a cylinder made of metal member of iron system housed in the holder member, a high-pressure seal part which forms said concave part as a pressurizing chamber by the pressure-contact of said holder member and said metallic pump housing on a plane intersecting in the direction where said plunger goes into and back by screwing up said holder member to said metallic pump housing, a plunger supported so as to be able to reciprocate, which goes into and back from said pressurizing chamber to pressurize fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber.
 8. The fluid pump according to claim 7, wherein said holder and said cylinder have a pressure-contact surface for receiving the fastening power when said holder is screwed up to the threaded part of said pump cylinder, wherein said cylinder is interposed and fixed between said pressure-contact surface and said high-pressure sealing surface, wherein a screw fastening part of said holder and said pump cylinder is formed within the range between said pressure-contact surface and said high-pressure sealing surface, and wherein a gap is formed between said cylinder and said holder inside said screw fastening part.
 9. The fluid pump according to claim 8, wherein a positioning part for determining the position in a radial direction of said holder and said cylinder is formed between the position of a pressure-contact surface of said holder and said cylinder and the position of said screw fastening part.
 10. The fluid pump according to claim 9, wherein the wall thickness of said holder in a radial direction at the position of said positioning part is thicker than wherein the wall thickness of said holder in a radial direction at the position of said screw fastening part.
 11. The fluid pump according to claim 8, wherein a gap is formed between the outer peripheries of said holders at the position where said positioning part is formed and said pump cylinder.
 12. A fluid pump comprising; a pump housing made of aluminum alloy having a concave part, in which the screw groove is formed on a surrounding wall of the open-end side of the concave part. a holder member engaged to said screw groove, a cylinder made of metal member of iron system housed in the holder member, a high-pressure seal part formed between said metallic pump housing and said cylinder which makes said concave part as a pressurizing chamber by screwing up said holder member to said metallic pump housing, a plunger supported so as to be able to reciprocate, which goes into and back from said pressurizing chamber to pressurize fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber. a fluid sealing mechanism installed between said plunger and an inner wall of said holder, and a seal element installed between the outer periphery of said holder and said pump housing, wherein the outer periphery of said cylinder is connected with a low-pressure fluid passage.
 13. A fluid pump comprising; a pump housing made of aluminum alloy in which a concave part is formed, a cylinder made of metal member of iron-system and installed in a concave part of the pump housing to divide the concave part into a pressurizing chamber and a low-pressure chamber, a plunger supported so as to be able to reciprocate, which goes into and back from said pressurizing chamber to pressurize fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber, a fluid sealing mechanism installed between said plunger and said pump housing on an open end side of said pump housing, and a seal element installed between the outer periphery of said holder and said pump housing, wherein the outer periphery of said cylinder is connected with a low-pressure fluid passage.
 14. A fluid pump comprising; a pump housing made of aluminum alloy in which a concave part is formed, a cylinder made of metal member of iron-system and installed in the pump housing to make the concave part as a pressurizing chamber by cooperating with the pump housing, a plunger supported so as to be able to reciprocate, which goes into and back from said pressurizing chamber to pressurize fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber.
 15. A fluid pump comprising; a first member having a concave part, a second member assembled with the first member to form said concave part as a fluid pressurizing chamber, a plunger supported by the second member so as to be able to reciprocate, which pressurizes the fluid in a pressurizing chamber, a seal part formed by the pressure-contact of said first and second members on a plane intersecting in the direction where said plunger is reciprocated, a pressing mechanism that presses said first and second members relatively against the plane intersecting in the direction where said plunger is reciprocated.
 16. A fluid pump comprising; a metallic pump housing having a concave part, a metallic tube body made of the metal member of which hardness is higher than said metallic pump housing, which forms said concave part as a fluid pressurizing chamber by assembling with said metallic pump housing, a plunger supported by said metallic tube body so as to be able to reciprocate in an axial direction, a seal part formed by the pressure-contact of said metallic pump housing and said metallic tube body on a plane intersecting in the direction where said plunger is reciprocated, a pressing mechanism that presses said metallic pump housing and said metallic tube body relatively toward said seal part.
 17. The fluid pump according to claim 15 or 16, wherein said first member and said metallic pump housing are made of the aluminum alloy, and said second member and said metallic tube body are made of iron-system alloys of which hardness is higher than aluminum alloy.
 18. The fluid pump according to claim 15 or 16, wherein spaces which allow the thermal deformation differences caused by the thermal expansion differences between said first and second members and between said metallic pump housing and said metallic tube body are provided between the inner periphery of said first member and the outer periphery of the second member and between the inner periphery of said metallic pump housing and the outer periphery of said metallic tube body.
 19. A fluid pump comprising; a metallic pump housing having a concave part, a screw groove formed to the inner wall of said metallic pump housing on the open-end side of said concave part, a holder member in which a threaded part that engages with the screw groove is formed in the outer periphery, a metallic tube body maintained in said holder member, which is installed in said metallic pump housing to form said concave part as a fluid pressurizing chamber, and a plunger supported so as to be able to reciprocate, which goes into and back from said pressurizing chamber. a seal part formed by the pressure-contact of said first and second members on a plane intersecting in the direction where said plunger is reciprocated by the engagement of said screw member and said metallic pump housing.
 20. A fluid pump comprising; a plunger, a plunger slide tube of wear-proof metal that supports so as to be able to slide and reciprocate the plunger, a base of wear-proof metal assembled so that said plunger slide tube can be detached, a seal part formed by the pressure-contact of said base and said plunge slide tube on a plane intersecting in the direction where said plunger is reciprocated, a pressing mechanism that presses said base and said plunge slide tube relatively toward said seal part.
 21. A fluid pump comprising; a plunger that reciprocates in a pressurizing chamber and pressurizes fluid, a cylindrical member of wear-proof that supports the plunger to be able to slide, a principal component of the plunger being iron. a pump body of wear-proof that forms a fluid pressurizing chamber by assembling said cylindrical member, a seal part formed by the pressure-contact of said pump body and said cylindrical member on a plane intersecting in the direction where said plunger goes forward and back, a pressing mechanism that presses said pump body and said cylindrical member relatively toward said seal part.
 22. The fluid pump according to claim 20 or 21, wherein said base and said pump body are made of aluminum alloy, and said plunger slide tube and said cylindrical member are made of harder iron-system alloy than aluminum alloy.
 23. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a seal part formed at the pressure-contact part between said pump housing and said cylinder, and a pressing mechanism which presses said pump housing and said cylinder relatively toward said seal part, a pressurizing chamber formed between said cylinder and said pump housing being sealed up at said seal part.
 24. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a pressurizing element by which fluid in pressurizing chamber formed between said cylinder and said pump housing or fluid is pressurized a sealing part formed by pressing said pump housing and said cylinder at a plane intersecting in a movement direction of said pressurizing element, a pressing mechanism that presses relatively said pump housing and said cylinder toward said sealing part.
 25. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a pressurizing element by which fluid in pressurizing chamber formed between said cylinder and said pump housing or fluid is pressurized, a metallic sealing part formed by pressing said pump housing and said cylinder at a plane intersecting in a movement direction of said pressurizing element, a pressing mechanism that presses relatively said pump housing and said cylinder toward said metallic sealing part.
 26. A fluid pump comprising; a pump housing, a cylinder combined with the pump housing, a pressurizing element by which fluid in pressurizing chamber formed between said cylinder and said pump housing or fluid is pressurized, sealing part formed at a plane intersecting in a movement direction of said pressurizing element, a pressing mechanism that presses relatively said pump housing and said cylinder toward said sealing part so that both are in non-contact state except said sealing part.
 27. A fluid pump comprising; a pump housing having a concave part, and a cylinder assembled in the concave part of the pump housing, wherein a gap is provided between opposing surfaces of the inner wall of said pump housing and said cylinder in a radial direction.
 28. A fluid pump formed by forming a concave part in the pump housing, assembling a cylinder member to the opening of said concave part and forming said concave part as a pressurizing chamber, providing a intake valve mechanism which supplies fluid to the pressurizing chamber and a delivery valve mechanism which takes out the pressurized fluid from the pressurizing chamber to said pump housing, pressurizing the fluid in said pressurizing chamber.
 29. A fluid pump formed by forming a concave part in the pump housing, assembling a cylinder member to the opening of said concave part and forming said concave part as a pressurizing chamber, providing a intake valve mechanism which supplies fluid to the pressurizing chamber and a delivery valve mechanism which takes out the pressurized fluid from the pressurizing chamber to said pump housing, pressurizing the fluid in said pressurizing chamber by a pressurizing element, wherein said cylinder is installed in said pump housing by engaging a holder member into which said cylinder is housed to a threaded part of said pump housing.
 30. A fluid pump comprising; a metallic pump housing having a concave part, a screw groove formed to the inner wall of said metallic pump housing on the open-end side of said concave part, a holder member in which a threaded part that engages with the screw groove is formed in the outer periphery, a metallic tube body maintained in said holder member, which is assembled with said metallic pump housing to form said concave part as a fluid pressurizing chamber.
 31. Afluid pump comprising; a pump housing made of aluminum alloy having a concave part, in which the screw groove is formed on a surrounding wall of the open-end side of the concave part. a holder member engaged to said screw groove, a cylinder made of metal member of iron system housed in the holder member, a seal part which forms said concave part as a pressurizing chamber by the pressure-contact of said holder member and said metallic pump housing on a plane intersecting in the direction where said plunger goes into and back by screwing up said holder member to said metallic pump housing, a pressurizing element that goes into and out from said pressurizing chamber and pressurizes fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber.
 32. The fluid pump according to claim 31, wherein said holder and said cylinder have a pressure-contact surface for receiving the fastening power when said holder is screwed up to the threaded part of said pump cylinder, wherein said cylinder is interposed and fixed between said pressure-contact surface and said seal part, wherein a screw fastening part of said holder and said pump cylinder is formed within the range between said pressure-contact surface and said seal part, and wherein a gap is formed between said cylinder and said holder inside said screw fastening part.
 33. The fluid pump according to claim 32, wherein a positioning part for determining the position in a radial direction of said holder and said cylinder is formed between the position of a pressure-contact surface of said holder and said cylinder and the position of said screw fastening part.
 34. The fluid pump according to claim 32, wherein the wall thickness of said holder in a radial direction at the position of said positioning part is thicker than wherein the wall thickness of said holder in a radial direction at the position of said screw fastening part.
 35. The fluid pump according to claim 32 or 33, wherein a gap is formed between the outer periphery of said holders at the position where said positioning part is formed and said pump cylinder.
 36. A fluid pump comprising; a pump housing made of aluminum alloy having a concave part, in which the screw groove is formed on a surrounding wall of the open-end side of the concave part. a holder member engaged to said screw groove, a cylinder made of metal member of iron system housed in the holder member, a seal part formed between said metallic pump housing and said cylinder which makes said concave part as a pressurizing chamber by screwing up said holder member to said metallic pump housing, a pressurizing element that goes into and out from said pressurizing chamber and pressurizes fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber. a fluid sealing mechanism installed between said plunger and an inner wall of said holder, and a seal element installed between the outer periphery of said holder and said pump housing, wherein the outer periphery of said cylinder is connected with a low-pressure fluid passage.
 37. A fluid pump comprising; a pump housing made of aluminum alloy in which a concave part is formed, a cylinder made of metal member of iron-system and installed in a concave part of the pump housing to divide the concave part into a pressurizing chamber and a low-pressure chamber, a pressurizing element that goes into and out from said pressurizing chamber and pressurizes fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber, a fluid sealing mechanism installed between said plunger and said pump housing on an open end side of said pump housing, and a seal element installed between the outer periphery of said holder and said pump housing, wherein the outer periphery of said cylinder is connected with a low-pressure fluid passage.
 38. A fluid pump comprising; a pump housing made of aluminum alloy in which a concave part is formed, a cylinder made of metal member of iron-system and installed in the pump housing to make the concave part as a pressurizing chamber by cooperating with the pump housing, a pressurizing element that goes into and out from said pressurizing chamber and pressurizes fluid, an intake valve mechanism installed in said pump housing, which supplies the fluid to said pressurizing chamber, a delivery valve mechanism installed in said pump housing, which takes out the pressurizing fluid in said pressurizing chamber.
 39. A fluid pump comprising; a first member having a concave part, a second member assembled with the first member to form said concave part as a fluid pressurizing chamber, a pressurizing element that goes into and out from said pressurizing chamber and pressurizes fluid, a seal part formed by the pressure-contact of said first and second members, a pressing mechanism that presses said first and second members relatively against the plane intersecting in the direction where said plunger is reciprocated.
 40. A fluid pump comprising; a metallic pump housing having a concave part, a metallic tube body made of the metal member of which hardness is higher than said metallic pump housing, which forms said concave part as a fluid pressurizing chamber by assembling with said metallic pump housing, a pressurizing element supported by said metallic tube body so as to be able to reciprocate in an axial direction, a seal part formed by the pressure-contact of said metallic pump housing and said metallic tube body on a plane intersecting in the direction where said pressurizing element is reciprocated, a pressing mechanism that presses said metallic pump housing and said metallic tube body relatively toward said seal part.
 41. The fluid pump according to claim 39 or 40, wherein said first member and said metallic pump housing are made of the aluminum alloy, and said second member and said metallic tube body are made of iron-system alloys of which hardness is higher than aluminum alloy.
 42. The fluid pump according to claim 39 or 40, wherein spaces which allow the thermal deformation differences caused by the thermal expansion differences between said first and second members and between said metallic pump housing and said metallic tube body are provided between the inner periphery of said first member and the outer periphery of the second member and between the inner periphery of said metallic pump housing and the outer periphery of said metallic tube body.
 43. A fluid pump comprising; a metallic pump housing having a concave part, a screw groove formed to the inner wall of said metallic pump housing on the open-end side of said concave part, a holder member in which a threaded part that engages with the screw groove is formed in the outer periphery, a metallic tube body maintained in said holder member, which is installed in said metallic pump housing to form said concave part as a fluid pressurizing chamber, and a pressurizing element that goes into and out from said pressurizing chamber and pressurizes fluid, a fluid seal part formed by the pressure-contact of said first and second members on a plane intersecting in the direction where said plunger is reciprocated by the engagement of said screw member and said metallic pump housing.
 44. A fluid pump comprising; a plunger, a plunger slide tube of wear-proof metal that supports so as to be able to slide and reciprocate the plunger, a base of wear-proof metal assembled so that said plunger slide tube can be detached, a seal part formed by the pressure-contact of said base and said plunge slide tube, a pressing mechanism that presses said base and said plunge slide tube relatively toward said seal part.
 45. A fluid pump comprising; a pressurizing element that reciprocates in a pressurizing chamber and pressurizes fluid, a cylindrical member of wear-proof that supports the plunger to be able to slide, a principal component of the pressurizing element being iron. a pump body of wear-proof that forms a fluid pressurizing chamber by assembling said cylindrical member, a seal part formed by the pressure-contact of said pump body and said cylindrical member on a plane intersecting in the direction where said pressurizing element goes forward and back, a pressing mechanism that presses said pump body and said cylindrical member relatively toward said seal part.
 46. The fluid pump according to claim 44 or 45, wherein said base and said pump body are made of the aluminum alloy, and said plunger slide tube and said cylindrical member are made of iron-system alloys of which hardness is higher than aluminum alloy.
 47. The fluid pump according to claim 41 to 46, wherein said fluid pump pressurizes the fluid from 5 to 20 mega Pascal.
 48. The fluid pump according to claim 41 to 46, wherein said fluid pump pressurizes gasoline from 5 to 20 mega Pascal. 